PUGWASH — Armed with loppers, saws and bug spray, a small army of volunteers slogged through slimy mud holes, clambered over fallen trees and swatted interminable swarms of mosquitoes on Sunday in their search for an invader near Pugwash.
Suddenly, there it was, all around them — the glossy buckthorn a nondescript shrub with speckled bark and shiny leaves, almost invisible among the alders, wild raisin, and serviceberry trees.
The glossy buckthorn may not be much to look at, but the introduced shrub has aggressively grown its way through much of the Pugwash Estuary Nature Reserve, pushing native species out of the way at this site, across Nova Scotia and elsewhere in North America.
“It doesn’t directly threaten the estuary or the wildlife in it,” volunteer Betty Hodgson explained as she trudged towards a grove of the unwanted trees with a crew of students, foresters, and conservationists. “But it does threaten the native plants that stabilize the land around the estuary. If they are gone, it could cause erosion and runoff that would threaten the fish and birds. It threatens the total ecology of the area.”
Glossy buckthorns produce blue-black seeds that are carried easily by birds and small mammals to other sites where the plants establish. The trees also produce a chemical that stops nearby trees from growing well, thus eliminating its competition for nutrients.
And when glossy buckthorns are chopped down, many more grow back from their roots, said Doug van Hemessen, stewardship co-ordinator for the Nature Conservancy of Canada.
“This is a job involving brute force,” he said of Sunday’s task.
The smallest saplings are grabbed tightly and pulled out – not as easy as it sounds because the roots may be tangled among older stumps. Bigger specimens, which can grow to about four metres tall and 10 centimetres thick, are sawn down or lopped off and their raw stumps sponged with herbicide to prevent the roots from sending up new shoots.
The herbicide is one of the most benign available: glysophate diluted with water and directed only at the raw wood stumps so it doesn’t affect other plants, said professional forester and licensed herbicide applicator Julia MacMillan, a licensed herbicide applicator. Although not the strongest herbicide available, it’s the most balanced choice for a conservation area, she said.
Once chopped down or tugged out of the ground, the trees must be hung upside down to prevent the cut ends and dangling roots from touching the earth and regrowing.
The .2 hectare (half-acre) attacked on Sunday was expected to give up some 5,000 stems, the same number removed from a plot beside it in 2013. The complete Pugwash Estuary Nature preserve measures almost 445 hectares (1,100 acres).
If the glossy buckthorn, a long-ago import from Eurasia, is left alone, it will push out native plants, said van Hemessen as he named the plants around him: serviceberry, wild raisin, star sarsaparilla, baneberry, star flowers, Canada mayflowers, several kinds of ferns, as well as maples and aspen.
“We’re trying to maintain our natural biodiversity,” he said.
EDITOR'S NOTE: This story has been updated with the following correction. Volunteer Betty Hodgson was originally misidentified as Betty Hodges. The story and cutline have been corrected.